Development of In-field Portable Sensor for Detection of Phosphates - - PowerPoint PPT Presentation

Development of In-field Portable Sensor for Detection of Phosphates and Heavy Metals in Everglades Water Systems.

Presented by: Shradha Prabhulkar Nanobioengineering/Bioelectronics Lab Biomedical Engineering Department Florida International University

Everglades Foundation Fellows - First Symposium January 13th , 2009

Introduction

• The Everglades National Park is the largest remaining subtropical

wilderness in the continental United States.

• These sub-tropical wetlands support a rich diversity of plants, fish and other
• animals. The Everglades support eight distinct ecosystems.
• However, the Everglades ecosystem is suffering due to human intervention

from as early as the late 1800s.

• In 1948, a massive project to provide flood protection and water

management for the ever growing South Florida human settlements was

• approved. More than 1,700 miles of canals and levees were built to divert

valuable freshwater from the wetlands into the sea. This interrupted the everglades natural sheet flow and caused the destruction of more than half the wetlands.

• While this project allowed the rapid growth of the region it worsened the

Everglade’s problems.

Historical Flow of water in Everglades Present Day Flow of water in Everglades

• In 2000, Congress approved a federal effort to restore the Everglades,

named the Comprehensive Everglades Restoration Plan (CERP), with the

• bjectives of restoration, preservation and protection of the South Florida

ecosystem while providing for other water related needs of the region".

• Besides rerouting water flow, reducing pollution and improving water quality

is also a major concern for the CERP.

• The southern part of the wetlands has been converted into agriculture land

for the growth of sugarcane. Phosphate containing fertilizers used in these fields get washed into the Everglades due to rainfall.

• Heavy metal pollution comes from the dumping of untreated storm water

discharge and street water discharge by the South Florida Water Management District into the Everglades.

• When it rains urban fertilizers, detergents, household chemicals, gas, oil

and other pollutants wash off roads, parking lots and driveways and are carried by storm water into drainage canals.

• Most pumping stations which treat the water before letting it flow into the

Everglades do not focus on the removal of heavy metals.

• Hence heavy metals such as lead, selenium, mercury, cadmium, arsenic
• etc. are accumulating in the waters of the everglades.
• Heavy metal toxicity disrupts natural ecosystems and affects the food chain,

leading to health problems in humans and animals.

• Heavy metals are hazardous even if they are present in extremely minute

quantities.

• The US EPA and the World Health Organization (WHO) lists them as a

known carcinogen.

• In the case of the Everglades, they lie in the path of trade winds, and the

climate is perfect for the type of thunderstorms that pull mercury out of the air.

• Gaseous mercury poured into the atmosphere naturally and by human

industry gets accumulated into the everglades.

• Around 900 pounds of gaseous mercury is dumped into the Everglades

each year.

• Twice as high Mercury levels found in parts of the Everglades, and in some
• f its animal population, is seven times higher than federal safety limits.
• Hence, the state of Florida warns against eating fish from the Everglades.

Regularly eating fish contaminated with mercury can cause brain damage and blindness in humans.

• Mercury can also be transferred from a pregnant mother to her child

Mercury Cycle in Everglades

Current Methods for Assessing Water Quality

• Surface water is monitored in a variety of locations, including canals,

pumping stations, agricultural discharges, and many other types of aquatic environments.

• Current monitoring methods are accomplished by invasively collecting

samples in the field and transporting them to centralized laboratories for analysis.

• Unfortunately, since contaminant specification or properties can be changed

quickly as a result of chemical, biological and physical reactions, the long time delays associated with this procedure are frequently unacceptable.

• Thus, one of the best preventive measures is to rapidly determine the

concentration of toxic compounds on-site.

• Advanced monitoring techniques such as ion chromatography , UV visible

spectrophotometry, X-ray absorption spectroscopy, atomic absorption spectrometry , and inductively coupled plasma-mass spectrometry are currently used for detection.

• But these techniques require large, expensive, sophisticated equipment that

can not typically be used in the field.

• Hence field assays which can provide highly sensitive, portable, easy to

use, real time detection of pollutants, at relatively inexpensive cost are needed.

Research Objectives

• The objective of my research is to develop a rapid, low cost, easy-to-use,

portable, multi-array sensor to measure various pollutants such as phosphates and heavy metals.

• The sensor will be based on a chip based platform enabling in-field usage.
• These sensors will provide the advantages of real time monitoring without

compromising on sensitivity.

• The sensors will also be cost effective and reusable.
• The use of a chip based platform will allow in-field, one-step, real time

detection of multiple pollutants.

Mechanism Of Detection

• Electrochemical methods will be used for the detection of phosphates

and heavy metals.

• The advantages of using Electrochemical detection methods:

1. Cost effective 2. Easy to use 3. Sensors can be miniaturized for in-field detection

• Electroactive materials. Oxidation or Reduction.
• The flow of electrons will generate a current which is proportional to the

concentration of the electroactive substance present in the water sample.

• The proposed sensor will be able to measure the current that will be

generated as a result of the flow of electrons. Concentration of analyte (ppb) Current (A)

TASK 1: To measure electroactivity of phosphates and heavy metals.

• Electrochemical experiments were conducted to test if phosphates and

heavy metals such as lead, selenium, mercury, cadmium, arsenic are electroactive.

• Commercially available phosphates and heavy metals were obtained and

dissolved in water. Gold electrodes were used to conduct voltammetric experiments using these samples.

• We observed that all the above mentioned pollutants are electroactive as

they undergo either reduction or oxidation at a certain potential. Hence at a certain potential either lose or gain electrons. This flow of electrons causes a current which can be measured by our proposed sensor.

Counter Electrode (Platinum) Reference Electrode (Ag/AgCl) Working Electrode (Gold)

C

e e e e

TASK 2: Design and Fabrication of Sensor Chip

TASK 3: Testing limits of detection for phosphates and heavy metals using fabricated chip

• We have tested sample solutions of phosphates and heavy metals using

the above mentioned fabricated chip.

• The lowest concentrations that we were able to measure were in the range
• f ppm (parts per million).
• However the concentration of pollutants in the Everglades system is in the

range of ppb (parts per billion).

• Hence we had to modify our procedure to measure lower concentrations.
• To enhance the sensitivity of our sensor we decided to use Magnetic

Nanoparticles.

• Magnetic nanoparticles coated with chemicals which show an affinity for

heavy metals will enable their preconcentration and highly sensitive detection using small sample volumes.

Pb Se Hg Ar Cd Cd Pb Ar Se Hg

Alkaline Phosphatase

Phosphate α-Glucose + H2O2 DMSA Magnet

Objectives Achieved

• Testing electroactivity of phosphates and heavy metals.
• Successful fabrication of sensor chip.
• Testing of sensor chip for detection of phosphates and

heavy metals. Calculated detection limit of sensor chip.

• Fabrication of gold nanoparticles and magnetic gold

nanoparticles.

• Coating gold nanoparticles with phosphate sensitive

enzyme – alkaline phosphatase.

• Coating magnetic gold nanoparticles with heavy metal

sensitive DMSA.

Work to be Done

• Test if using magnetic nanoparticles is helping to reduce the detection limit

for phosphates and heavy metals.

• Testing fabricated sensor using real water samples from various sites in the

Everglades such as Okeechobee lake.

• The results obtained using the portable in-field sensors will be compared to

the concentration of pollutants obtained using the current gold standard laboratory techniques.

• This will enable us to verify the performance of our sensors.
• Successful development of this portable multi-analyte chip based sensing

system may have broad applications for monitoring surface water, sediments, wastewater treatment, and bioreactors where small size and ability to measure multiple analytes is desired.

• The novelty of our research lies in the use of nanoparticles which can be

help detection miniscule amounts of pollutants.

• The ability to measure multiple analytes using a single sensor chip will

unable hassle free, rapid monitoring.

• The Everglades Fellowship, has helped me pursue my dissertation

project and achieve my research objectives.

• The Fellowship will further allow me to get a hands-on, in-field

experience for testing our sensor.

• Testing of our sensor in the Everglades will provide valuable

information about the its performance.

• The Fellowship has funded my research for the past one year in

terms of tuition payment, purchase of lab supplies.

• The research funded by this Fellowship has been published as a full

journal paper in “ Biosensors and Bioelectronics”.

• A part of the Fellowship funding will be used to enable me to attend

Pittcon Conference and Expo 2010 to be held in Orlando, Fl to showcase my research findings.

Everglades Fellowship

Acknowledgements

• Everglades Foundation
• Dr. Chenzhong Li
• Lab Members

Thank You